I ordered a 2014 JKU Sport for my wife last night. I hadent even thought about the gearing untill this morning. I own a TJ and 3.21's sound horrible to me but I understand that its a much different platform so I need opinions. This will most likely stay stock as my wife will be driving it and if it ever goes offroad the extent will be the beach and dirt roads to camp, no crawling or mud. It has the stock 17's with the 255/75/17's, would upgrade to 33's at most. We do go to Vermont a few times a year and an occasional trip to georgia so we deal with some mountain roads but also alot of highway miles. I want this rig to get better mpg but I also dont want it to be a complete dog because of it. The jeep is on order and will take 6-8 weeks so Im assuming if I call today I could still get this change made and I dont believe there is a cost involved. What do you guys get for mileage (or did when it was stockish) how was the driving experience with either one? Im on the fence.
Help- JKU 3.21 vs 3.73 Opinions
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if you're gonna stick with street tires, then the 3.21 gears are preferred... better gas mileage. But, if you plan on going to large tires, then get the 3.73 gears. 33s are only marginally larger than stock 255/75/17 (32") so for a 99% on-road Jeep (like most daily drivers are), then I'd even suggest sticking with the 3.21 gears for local terrain. In areas with hills, 3.73 would be better, but... we're on the east coast.
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if you're gonna stick with street tires, then the 3.21 gears are preferred... better gas mileage. But, if you plan on going to large tires, then get the 3.73 gears. 33s are only marginally larger than stock 255/75/17 (32") so for a 99% on-road Jeep (like most daily drivers are), then I'd even suggest sticking with the 3.21 gears for local terrain. In areas with hills, 3.73 would be better, but... we're on the east coast. I agree. I have 3.21 and im running a heavy 34" tire and I need to regear when I jump to 35s. When I drive my wifes stock JK with the same 3.21 gears you can tell the difference. With a 33" tire you will be just fine with the stock 3.21 gears and like Jerry said you cant beat the MPG. The wife gets 19-20 around town and has pushed 26 mpg on the highway. Even with my 34s and 3.21 gears I average 17 about town and 20 on the highway which is not bad with the added weight of larger wheels, tires, skid plates, and accessories I have added.
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If it's a stick you might want to consider 3.73s. I drove both before I bought and I found that with the 3.21s you have to spend more time in lower gears, negating the effect of the taller ratio. Accelerating to pass from 55 mph required a downshift with the 3.21s, just a push on the gas with the 3.73s.
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To jump on this topic, is there a stock gearing configuration that is tolerable on 35" tires? Most JKU's seem to come with 3.21 gears but if 4.10 is fine for 35" tires then would it be worth it to find one with those gears? Also, are 4.10 gears even available in a JKU that isn't a Rubicon? I'm speaking specifically of the 2012-2014 model years.
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To jump on this topic, is there a stock gearing configuration that is tolerable on 35" tires? Most JKU's seem to come with 3.21 gears but if 4.10 is fine for 35" tires then would it be worth it to find one with those gears? Also, are 4.10 gears even available in a JKU that isn't a Rubicon? I'm speaking specifically of the 2012-2014 model years.i think the 4.10 is only on the rubicon..possibly the fully loaded MOAB as it has a rear locker option i think.
my 33's on 3.73's (tow package) cruises at 2500RPM @ 70mph. and i maintain 18MPG. (calculated). Towing a 3200lb boat, i get 14-15 and can maintain highway speeds without much thought...mountains are still pretty decent (45-50MPH on 7% grade) without feeling like i'm going to blow anything up.
i would imagine 35's on 4.10's would be similar.
adams jeep of aberdeen only orders the 3.73 tow packages if they plan on lifting/tires (33's or 35's) and most people are happy with the setup.
if not for the fact i tow with my JKU, i would not hesitate to put 35's on 3.73's knowing i would loose some highway gas mileage.....
that being said...33's on 3.21's would be fine too in my book.
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So basically if a person was hoping to run 35" tires they should steer far clear of one with 3.21 gearing unless they expect to regear to say 4.10 gears? Eventually we'd like to have a JKU and if my past history is any indicator we'll be lifting it almost immediately. I'm not against regearing a Jeep (did my TJ when it only had 15k miles on it) to have everything working well but if I can find a combination that doesn't require me spending lots of extra money then I'm all for that. Even though this one will be primarily driven on the street with some time on the beach I still don't want it to be a dog. Nothing is more frustrating than an underpowered vehicle. Thanks Dave!
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yes. 35's and 3.21's IMO would not be very DD friendly. 3.73's with 35's are a common setup that many seem to be happy with. I would think 4.10's on 35's would be ideal.
FWIW the new (2012+) 3.6 engine is great (once you get past the fact it's not a 4.0 LOL), so research may say otherwise if they have the older 3.8 many go to 5.13-5.38's with 35's...crazy
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late reply since I was out on the road... but if you can spring for the Rubicon, order it with the 4.10 gears and it'll be pretty nice for the flat Delaware roads. I debated which gears to get with mine, but decided to stick with 3.73s since I intended to stick with the stock tires for a while and didn't want to kill the gas mileage too much. I know I'll feel it when I finally bump up to 35s, but it won't be too bad... I was pulling 80mph uphill out in the western MD hills.
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